Chemical and Complementary Role of Fluorine in a Chlorine Based Reactive Ion Etching of GaN

Conventional reactive ion etching of epitaxially grown GaN on (0001) sapphire substrate has been investigated using a basic chemistry of SiCl4, Ar and SF6. Photoresist or plasma-deposited SiNx were used for masking. The influence of gas flow, pressure and rf-power on the etch rate and morphology were studied. A maximum etch rate of 430 nm/min was obtained at an rf power of 300 W. Very smooth surfaces and reasonable etch rates (±100 nm/min) were obtained using the same chemistry at a lower rf-power of 105 W (dc bias of ±290 V). The chemical and complementary roles of chlorine and fluorine will be demonstrated